Drag trowel with counterweight means

ABSTRACT

A drag trowel device having a plurality of leaves which contact the interior surfaces of a pipe coated with a lining substance to effect the trowelling of same. The leaves are mounted on one end of a longitudinal lever arm and a counterweight is mounted at its other end. The lever arm is pivotally connected at an intermediate location thereon to a pulling means. The counterweight serves to cancel the net weight of the trowel itself so that the trowelling pressure exerted by the leaves will be the same along the top and bottom of the pipe.

United States Patent [191 Nelson Holland DRAG TROWEL WITH COUNTERWEIGHTMEANS [75] Inventor: Henry A. Nelson Holland, Houston,

Tex.

[73] Assignee: Raymond International, Inc.,

Houston, Tex.

[22] Filed: Mar. 11, 1974 [21] App]. No.: 450,161

52 us. Cl. 425/95; 425/262; 425/460 [51] Int. Cl. B28B 21/94 [58] Fieldof Search 425/59, 95, 262, 457, 460, 425/469 56] References Cited UNITEDSTATES PATENTS.

2,261,928 11/1941 Perkins et a1. 425/262 2,484,018 10/1949 Crom 264/2703,108,348 10/1963 Schultz 425/262 3,167,837 2/1965 Matheny 425/460 Nov.18, 1975 3,263,296 8/1966 Barton 425/460 3,334,389 8/1967 Matheny....3,384,940 5/1968 Barton 425/262 Primary Examiner-Francis S. HusarAssistant Examiner-John MCQuade Attorney, Agent, or Firm-Fritzpatrick,Cella, Harper & Scinto [57] ABSTRACT A drag trowel device having aplurality of leaves which contact the interior surfaces of a pipe coatedwith a lining substance to effect the trowelling of same. The leaves aremounted on one end of a longitudinal lever arm and a counterweight ismounted at its other end. The lever arm is pivotally connected at anintermediate location thereon to a pulling means. The counterweightserves to cancel the net weight of the trowel itself so that thetrowelling pressure exerted by the leaves will be the same along the topand bottom of the pipe.

28 Claims, 3 Drawing Figures US. .Patent Nov. 18, 1975 Sheet 2 of 33,920,363

I I I H DRAG TROWEL WITH COUNTERWEIGHT MEANS This invention relates toan improved drag trowel device and, more specifically, to such a devicewhich employs a novel means of positioning and mounting trowel leaves soas to effect more uniform trowelling of the interior walls of pipes,tubes and other conduits.

The present invention is suited foruse with lining machines which coatthe intcrior walls of pipes and the like with plastic or mortar-likesubstances. These lining machines have a spray or distributor head whichrotates at speeds approaching two thousand revolutions per minute whilethe lining machine is pulled through the pipe or conduit. This highspeed rotation causes the lining substance to be flung outwardly bycentrifugal action so that it becomes deposited on the conduit wall. Atrowelling device is moved along behind the distributor head; andvarious leaf-like trowelling elements mounted on the trowelling devicewipe along the conduit walls to smooth out the deposited material. Thetrowelling elements are spring biased radially against the interiorwalls to ensure full trowelling of the deposited material.

In the past, certain problems have been encountered in the use of thesetrowelling devices. More particularly, it has been difficult to maintaineven trowelling pressure around the conduit being lined. In most priorart arrangements, the trowelling device was coupled to .thedepositingdevice by means of a flexible connection. However, this wasdisadvantageous because, the weight of the trowelling device would addto the downward leaf pressure so that the bottom of the conduit wastrowelled more severely than the other regions. On the other hand, itwould not be practical to mount the trowelling device to extend outcantilever fashion behind the material depositing device because in suchcase the conduit irregularities, i.e. turns or dips, encountered by thematerial depositing device would cause it to swing the trowelling devicequite severely and in a manner unrelated to the particular conduitirregularities in the vicinity of the trowelling device.

The present invention overcomes the above described problems and permitsthe trowelling of conduit interiors in a smooth and uniform manner. Thetrowelling obtained through the present invention is not effected by theweight of the trowelling device nor is it subject to the'movements ofthe material depositing mechanism to which it is coupled.

According to the present invention there is provided a novel dragtrowelling arrangement wherein a drag trowelling assembly is mountedtoward one end of .a longitudinally disposed lever arm. A counterweightis mounted on the lever arm toward its other end and a swivel connectionto a material depositing device or are applied around the interior ofthe conduit. Also,'

any movements of the swivel connection away from the axis of the conduitwill be accomodated automatically by a swinging of the lever arm aboutthe swivelconnection and a corresponding countermovement of thetrowelling assembly so that: it will remain centered and continue toexert even trowelling pressure around the conduit interior.

As will be described more fully hereinafter, the present invention, incertain aspects, involves arrangements in which a plurality of tandemlydisposed trowelling assemblies are mounted as above described to obtainrough and finish trowelling. Also, according to one embodiment the twotrowelling assemblies are mounted on a common arm which itself ispivoted to the lever arm so as toimprove the balancing of trowellingforces and to maintain proper orientation of the trowelling device. i

There has thus been outlined rather broadly the more important featuresof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention thatwill be described more fully,hereinafter. Those skilled in the art will appreciate that theconception onwhich this disclosure is based may readily be utilized asthe basis of the designing of other structures for carryingout thepurposes of this invention. It is important, therefore, that thisdisclosure be regarded as including such equivalent constructions as tonot depart from the spirit and scope of the invention. I

Cetain specific embodiments of this invention have been chosen forpurpose of illustration and description, and are shown intheaccompanying drawings, forming a partof the specification, wherein:

FIG. 1 is an elevation view,'partially in section, showing a drag troweldevice in which the present invention is embodied:

FIG. 2 is aview similar to FIG. 1 but showing a modified form of thedrag'trowel device of the present invention; and v 2 FIG. 3 is a viewsimilar to FIG. 2, but showing a still further modified form of the dragtrowel device of the present invention. 1

As shown in FIG. 1 a conduit 10, such as a pipe, is provided with alining 12 of a castable material, such as cement or mortar, whichreconditions the pipe by sealing any leaks and allowing smooth and freefluid flow therethrough without further corrosion.

The lining 12 is applied by'a combination depositing and trowellingmachine 14 which is pulled lengthwise through the pipe 10. Thedepositing and trowelling machine 14 comprises a material depositingmechanism 16 and a trowellingdevice 18 which is attached to and followsthe materialdepositing mechanismthrough the pipe. The materialdepositing mechanism 16 includes a housing 20 which contains materialfeed arrangements and drive motors for depositing the lining material.Wheels 22, or equivalent support elements, extend from the pipe 10 tohold the material depositing mechanism 16 centered in the pipe as itispulled through the pipe by any suitable means (not shown).

The material depositing mechanism 16 also includes a rotary distributionhead 24 extending from behind the mechanism. This head rotates at highvelocity, e.g. at 2000 revolutions per minute and thereby causes a wetfluent lining material 26, such as cement or cementmortar, to be throwncentrifugally outward so that it becomes deposited on the inner surfaceof the pipe 10 in the form of a rough lining 12a. This rough lining 12ais then acted upon by the trowelling device 18 as it moves along behindthe material depositingmechanism 3 l6; and the trowelling device 18smooths out the rough lining 120 before it hardens so that there isformed the smooth lining 12.

The trowelling device 18 comprises a frame 28 made up of a conical ring30 somewhat smaller in diameter than the pipe 10, a hollow central axialshaft 32 and a plurality of spokes 34 and 36 extending, respectively,from the front and rear of the shaft 32 to the conical ring 30. Aplurality of sheet metal trowelling leaves 28 are mounted in overlappingarray about the conical ring 30; and each leaf is secured to the ring 30by means of a pivot 40. The trowelling leaves 38 extend out behind thering 30 and their pivots 40 are so oriented that as the leaves swingabout them their rearward edges flare outwardly more or less toaccommodate different pipe diameters.

' A bias spring 42 is provided to urge the trowelling leaves outwardlyagainst the interior surface of the pipe 10. This bias spring 42 is acoil spring bent around to form a torus which fits inside the overlappedtrowelling leaves; and it is secured to the ring 30 by means of wires 44which extend forwardly from the spring to the pivots The trowellingdevice 18 is connected to the material distributing mechanism 16 bymeans of a coupling device 46. This coupling device comprises a bracketin the form of cup shaped housing 48 having its open end flanged andsecured, by means of screws 50, to a plate 52 mounted at the rear of thedistributor head 24. The base of the cup shaped housing 48 is formedwith a ball socket 54. This socket accommodates a ball formation 56located along the length of a rod-like mounting lever 58. The mountinglever passes through the base of the cup shaped housing 48 andterminates near the plate 50. The'housing 48 thus serves as a bracket toconnect the mounting lever pivotally near its central region to thedistributor head 24. A cylindrical counterweight 60 is fitted onto themounting lever 58 within the housing 48; and the distance of thecounterweight from the ball and socket joint, formed by the socket 54and the ball formation 56, can be adjusted simply by moving thecounterweight along the length of the mounting lever and securing it inplace with a setscrew (not shown). It will be seen that thecounterweight 60 is free to move inside the cup shaped housing 48 as themounting lever 58 pivots at the ball and socket connection 54, 56. Thecounterweight may also be threaded onto the lever 58 and adjusted simplyby rotating it on the lever.

The portion of the mounting lever 58 which projects beyond the base ofthe cup shaped housing 48 extends into and through the central axialshaft 32 of the troweling device 18. The rearward tip of the lever 58 isthreaded; and a washer 62 and a nut 64 are provided on it to hold theshaft 32 onto the lever. This allows free rotation of the shaft 32 andthe trowelling device 18 on the lever 58.

It will be appreciated that the ball and socket joint formed by thesocket 54 and the ball formation 56, serves both as a swivel and as alever fulcrum for the lever 58. The lever 58 is weighted on one side ofthis fulcrum by the trowelling device 18; and it is weighted on theopposite side of the fulcrum by the counterweight 60. By properadjustment of the location of the counterweight 60 along the lever arm58, as above described, the weight of the trowelling device 18 can beprecisely balanced. As a result, the weight of the trowelling device 18is not supported by the trowelling leaves 38 but instead it is supportedby the material depositing mechanism 16 acting through the lever armfulcrum. Because of this the only outward forces exerted by thetroweling leaves on the interior of the pipe 10 are those which areproduced by the bias spring 42; and these forces are equally distributedin all radial directions. At the same time the troweling device is freeto move up or down or sideways as the combination depositing andtrowelling machine 14 passes over inclines, dips or curves in the pipe10.

In operation of the above described combination depositing andtrowelling machine 14, the material depositing mechanism 16 is pulledthrough the interior of the pipe 10 by any known means, while the wheels22, which ride along the inner surfaces of the pipe, serve to maintainthe rotary distributor head 24 centered in alignment with the pipe axis.Thus, as the distributor head rotates while moving along through thepipe 10, it throws lining material 26 out against the inner walls of thepipe to form the uniformly distributed, though rough, lining 12a.

As the trowelling device 18 is pulled along behind the materialdepositing mechanism 16, the leaves 38 of the trowelling device pressoutwardly against the rought lining 12a and smooth it to form thefinished lining 12. Because of the above described counterbalancingprovided by the coupling device 46, the weight of the trowelling device18 is not transmitted through the trowelling leaves 38; and accordinglyan even trowelling pressure is exerted in all radial directions so thatthe thickness of the finished lining 12 is uniform all about the pipeinterior. At the same time should the depositing and trowelling machine14 pass through inclines, dips or curves in the pipe 10, the pivotingcharacteristic of the coupling device will allow the leaves of thetrowelling device to remain centered in the pipe even though the fulcrumpoint of the lever arm 58 may temporarily be shifted away from the pipeaxis.

-In certain instances, the material depositing mechanism 16 does nothave a separate plate such as the plate 52 extending beyond the rotarydistributor head 24. Accordingly, it becomes necessary in such instancesto mount the drag trowel directly to the rear face of the rotarydistributor head 24. Since these distributor heads rotate typically atabout two thousand revolutions per minute, it becomes necessary toprovide special rotary bearing arrangements which allow the drag trowelto move through the pipe 10 without rotation. Such an arrangement isillustrated in FIG. 2. As can be seen in FIG. 2, there is provided amounting plate on the rear face of the rotary distributor head 24. Atapered conically shaped housing 72 is affixed to the mounting plate 70to rotate with it and with the rotary distributor head 24. The housing72, as shown, tapers rearwardly toward the axis of the device. The outerrace of a ball bearing assembly 74 is mounted toward the rearward end ofthe housing 72. The inner race of the ball bearing assembly 74, asshown, is formed with a ball socket 76 which accommodates a ballformation 78 of a mounting lever 80. The mounting lever 80 is similar instructure and operation to the lever arm 58 of the preceding embodiment.Also, the remainder of the elements forming the coupling device are thesame as in the embodiment of FIG. 1. Thus the housing 72 serves as abracket to connect the mounting lever pivotally near its central regionto the distributor head 24.

The arrangment of FIG. 2, however, allows very rapid rotation of theconically shaped housing 72 while the mounting lever 80 remains freefrom such rotation; al-

5 though, it is free to swivel .in the ball and socket formationdefinedby the socket .76 and the ball formation 78.

The embodiment of FIG. 2 provides an additional refinement whereby bothrough and finish trowelling can be accomplished Simultaneously.According to this refinement, there is provided a second or rearwardtrowelling frame assembly 81 made up of a rearward conical ring 82 andspokes 84, which extend from the ring 82 to the rearward end of theshaft 32. This assembly is rigidly mounted by means of struts-86 securedto spokes 88 which in turn extend between the forward conical ring 30and the hollow a-xial shaft 32. As can be seen in FIG. 2, the mountinglever 80 extends completely through the axial shaft 32, as in thepreceding embodiment, and it is secured there by means of a nut andwasher assembly 62, 64 as described above.

The rearward trowelling assembly 81 is of substantially the sameconstruction as the forward trowelling assembly 18. As shown, therearward trowelling assembly 81 comprises trowelling leaves 86, whichare connected to the conical ring 82 by means of pivots 88. These leavesare biased radially in an outward direction by means of acircumferential bias spring 90. The spring 90 is also secured to therearward conical ring 82 by means of wires 92 extending between thepivots 88 and the spring.

It will be noted from FIG. 2 that the trowelling leaves 86 are instaggered relationship withrespect to the leaves 38 of the forwardtrowelling assembly. Thus, any irregularities which may be left by theforward trowelling assembly are smoothed out by the subsequent passageof the rearward. trowelling assembly 81. In addition, the bias spring 90may be more lightly stressed than the bias spring 42 of the forwardtrowelling assembly so that a lighter finishing trowelling action can beobtained.

The two trowelling assemblies are rigidly mounted with respect to eachother; however, they are free to pivot as a unit about the fulcrum pointof the mounting lever 80 defined by the ball and socket assemblys76, 78.The counterweight 60 may be adjusted, as in the preceding embodiment, tocounterbalance the net weight of the two sets of trowelling leaves.

The embodiment of FIG. 3 provides a further refinement which allows twosets of trowelling leaves tobe mounted rigidly with respect to eachother and yet permits a more flexible pivoting acting so that the devicemay follow a sharper curvature in the pipe 10. As can 'be seen in FIG.3, the overall structure of the two trowelling assemblies issubstantially the same as that described above in connection with FIG.2. However, in

the arrangement of FIG. 3, there is provided a large diameter hollowaxial shaft 100 which replaces the axial shaft 32 of the preceding.embodiments. The large diameter hollow axial shaft 100 is rigidlyconnected to, and forms a portion of, the frame and strut assemblies ofthe forward and rearward trowelling assemblies. The

mounting lever 80 extends back through the center of 6 mechanism movesaround a curvature or a dip in a pipe can be visualized by consideringthe rotary, distributor head 24 to have moved upwardly from its normalposition along the pipe centerline as shown in FIG. 3. This movementoccurs, for example, when the distributing mechanism moves into a dip.in the pipe 10. This upward movement causes the ball and socket pivot74, 76 to moveupwardly. However, the trowelling assemblies 18 and 81remain in position while the mounting lever 80 pivots to move thecounterweight 60 to its phantom line position. It will also be seen,that the orientation of the trowelling assemblies 18 and 81 is notaffected. by this movement. Instead they remain aligned along thecenterline of the pipe 10 in the region they happen to be trowelling.This is due to the fact that the pivot 104 allows the orientation of thetrowelling assemblies 18 and 81 to remain independent of the angularposition assumed by the mounting lever 80. Instead, the align- In orderto ensure thatthe two trowelling assemblies I exert balanced forcesagainst) the pipe. being trowelled they should be maintained balancedwith respect tothe pivot 104. This balancing may be precisely controlledand maintained, as shown in FIG. 3, by means of a balance ring 106 whichfits over and is slideable along the hollow axial shaft 100. The balancering 106 is moved back and forth until the overall weight distributionof the two trowellingassemblies 18 and 81 and the hollow axial shaftwith the ring 106 is balanced with respect to the pivot 104. The ring106 may then be secured in place with a setscrew 108.

Although particular. embodiments of the invention are herein disclosedfor purposes of explanation, various modifications thereof, after studyof this specification, will be apparent to those skilled in the art towhich the invention pertains.

.What is claimed and desired to be secured by Letters Patent is:

1. A drag trowelling device comprising a frame, trowelling leavessupported from said frame, an elongated lever arm, said frame beingmounted at a first location on said lever arm, counterweight means toneutralize the net weight of the frame and trowelling leaves, saidcounterweight means being mounted at a second location on said arm andsupport means including a pivot supporting said arm for swingingmovement about a third location intermediate said first and secondlocations.

2. A drag trowelling device according to claim l wherein saidcounterweight means is adjustably positionable along said lever arm.

3. A drag trowelling device according to claim 2 wherein saidcounterweight means. is provided with locking means for securing it tosaid lever arm at different locations along its length.

4. A drag trowelling device according to claim 1 wherein said trowellingleaves are resiliently biased in radial outward directions.

5. A drag trowelling device according to claim 1 wherein said frame ismounted for free rotation about said lever arm about its longitudinalaxis.

6. A drag trowelling device according to claim 1 wherein said pivot isconstructed to allow swinging movement of said lever arm in alldirections radial of its axis.

7. A drag trowelling device according to claim 1 wherein said pivotcomprises a ball and socket construction.

8. A drag trowelling device according to claim 1 wherein said pivotincludes a bearing permitting free rotational movement of said lever armabout its axis.

9. A drag trowelling device according to claim 1 wherein said framesupports plural sets of trowelling leaves.

10. A drag trowelling device according to claim 9 wherein said frame ispivotally connected to said lever arm at a location intermediate saidsets of trowelling leaves.

11. A drag trowelling device comprising a support member, centeringmeans for maintaining said support member generally centered within atubular conduit as it is pulled through the conduit, an elongated leverarm, connector means pivotally connecting said lever arm, at a locationthereon intermediate its ends, to said support member, trowel meansmounted on the elongated lever arm on one side of the said location andcounterweight means to neutralize the net weight of the trowel means,said counterweight means being mounted on the elongated lever arm on theother side of said location. i

12. A drag trowelling device according to claim 11 wherein said supportmember includes means for contacting the interior of a conduit formaintaining said support member substantially centered therein.

13. A drag trowelling device according to claim 11 wherein saidconnector means comprises a swivel allowing both swinging and rotarymovement of said lever arm.

14. A drag trowelling device according to claim 11 wherein saidconnector means includes a ball and socket construction.

15. A drag trowelling device according to claim 14 wherein saidconnector means further includes rotary bearing means allowing freerotation of said support member with respect to said lever arm.

16. A drag trowelling device according to claim 11 wherein saidconnector means includes a generally cup shaped housing having its openend secured to said support member and its base pivotally connected tosaid lever arm.

17. A drag trowelling device according to claim 16 wherein said leverarm extends through the base of said housing and wherein saidcounterweight means is positioned between the walls of said housing.

18. A drag trowelling device according to claim 17 wherein the base ofsaid housing is connected to the outer race of a rotary bearing having arotational axis extending along .the longitudinal axis established bysaid centering means and a ball and socket structure connected to theinner race of said bearing.

19. A drag trowelling device according to claim 11 wherein said supportmember is a portion of a lining depositing device.

20. A conduit lining mechanism comprising a lining material depositingmechanism operable, when dragged through a conduit, to impel hardenableliner material onto the interior walls of the conduit, trowelling meanshaving a plurality of trowel elements biased radially outwardly to pressupon and smooth out the deposited liner material when the trowellingmeans is pulled along through the conduit behind the material depositingmechanism and coupling means connecting said trowelling means to saidmaterial depositing mechanism to be pulled along behind it, saidconnecting means comprising a support bracket secured to and extendingout behind the depositing mechanism, an elongated lever arm extendinggenerally axially of said trowelling mechanism, means pivotallyconnecting said lever arm, at a location thereon intermediate its ends,to said support bracket, said trowelling means being attached to theelongated lever arm on one side of said location and counterweight meansto neutralize the net weight of the trowelling means, said counterweightmeans being mounted on said elongated lever arm on the other side ofsaid location.

21. A conduit lining mechanism according to claim 20 wherein saidsupport bracket is in the form of a cup shaped housing having its openend mounted on the material depositing mechanism and having secured toits opposite end said means pivotally connecting said lever arm.

22. A conduit lining mechanism according to claim 20 wherein saidtrowelling means comprises a frame supporting two sets of trowellingleaves tandemly thereon.

23. A conduit lining mechanism according to claim 22 wherein saidtrowelling means includes a central axially extending member from whichradial elements extend to support said trowel elements.

, 24. A conduit lining mechanism according to claim 23 wherein saidtrowelling means is attached to said lever arm at said central axiallyextending member.

25. A conduit lining mechanism according to claim 24 wherein saidtrowelling means is attached to said central axially extending member ata location thereon intermediate said two sets of trowelling leaves.

26. A conduit lining mechanism according to claim 25 wherein said leverarm is pivotally attached to said central axially extending member.

27. A conduit lining mechanism according to claim 26 wherein saidcentral axially extending member is tubular and of substantially largerdiameter than said lever arm, said lever arm extending inside saidmember and pivotally secured to an inner flange in said member.

28. A conduit lining mechanism according to claim 27 wherein saidcentral axially extending member includes a balance weightlongitudinally adjustable there-

1. A drag trowelling device comprising a frame, trowelling leavessupported from said frame, an elongated lever arm, said frame beingmounted at a first location on said lever arm, counterweight means toneutralize the net weight of the frame and trowelling leaves, saidcounterweight means being mounted at a second location on said arm andsupport means including a pivot supporting said arm for swingingmovement about a third location intermediate said first and secondlocations.
 2. A drag trowelling device according to claim 1 wherein saidcounterweight means is adjustably positionable along said lever arm. 3.A drag trowelling device according to claim 2 wherein said counterweightmeans is provided with locking means for securing it to said lever armat different locations along its length.
 4. A drag trowelling deviceaccording to claim 1 wherein said trowelling leaves are resilientlybiased in radial outward directions.
 5. A drag trowelling deviceaccording to claim 1 wherein said frame is mounted for free rotationabout said lever arm about its longitudinal axis.
 6. A drag trowellingdevice according to claim 1 wherein said pivot is constructed to allowswinging movement of said lever arm in all directions radial of itsaxis.
 7. A drag trowelling device according to claim 1 wherein saidpivot comprises a ball and socket construction.
 8. A drag trowellingdevice according to claim 1 wherein said pivot includes a bearingpermitting free rotational movement of said lever arm about its axis. 9.A drag trowelling device according to claim 1 wherein said framesupports plural sets of trowelling leaves.
 10. A drag trowelling deviceaccording to claim 9 wherein said frame is pivotally connected to saidlever arm at a location intermediate said sets of trowelling leaves. 11.A drag trowelling device comprising a support member, centering meansfor maintaining said support member generally centered within a tubularconduit as it is pulled through the conduit, an elongated lever arm,connector means pivotally connecting said lever arm, at a locationthereon intermediate its ends, to said support member, trowel meansmounted on the elongated lever arm on one side of the said location andcounterweight means to neutralize the net weight of the trowel means,said counterweight means being mounted on the elongated lever arm on theother side of said location.
 12. A drag trowelling device according toclaim 11 wherein said support member includes means for contacting theinterior of a conduit for maintaining said support member substantiallycentered therein.
 13. A drag trowelling device according to claim 11wherein said connector means comprises a swivel allowing both swingingand rotary movement of said lever arm.
 14. A drag trowelling deviceaccording to claim 11 wherein said connector means includes a ball andsocket construction.
 15. A drag trowelling devIce according to claim 14wherein said connector means further includes rotary bearing meansallowing free rotation of said support member with respect to said leverarm.
 16. A drag trowelling device according to claim 11 wherein saidconnector means includes a generally cup-shaped housing having its openend secured to said support member and its base pivotally connected tosaid lever arm.
 17. A drag trowelling device according to claim 16wherein said lever arm extends through the base of said housing andwherein said counterweight means is positioned between the walls of saidhousing.
 18. A drag trowelling device according to claim 17 wherein thebase of said housing is connected to the outer race of a rotary bearinghaving a rotational axis extending along the longitudinal axisestablished by said centering means and a ball and socket structureconnected to the inner race of said bearing.
 19. A drag trowellingdevice according to claim 11 wherein said support member is a portion ofa lining depositing device.
 20. A conduit lining mechanism comprising alining material depositing mechanism operable, when dragged through aconduit, to impel hardenable liner material onto the interior walls ofthe conduit, trowelling means having a plurality of trowel elementsbiased radially outwardly to press upon and smooth out the depositedliner material when the trowelling means is pulled along through theconduit behind the material depositing mechanism and coupling meansconnecting said trowelling means to said material depositing mechanismto be pulled along behind it, said connecting means comprising a supportbracket secured to and extending out behind the depositing mechanism, anelongated lever arm extending generally axially of said trowellingmechanism, means pivotally connecting said lever arm, at a locationthereon intermediate its ends, to said support bracket, said trowellingmeans being attached to the elongated lever arm on one side of saidlocation and counterweight means to neutralize the net weight of thetrowelling means, said counterweight means being mounted on saidelongated lever arm on the other side of said location.
 21. A conduitlining mechanism according to claim 20 wherein said support bracket isin the form of a cup shaped housing having its open end mounted on thematerial depositing mechanism and having secured to its opposite endsaid means pivotally connecting said lever arm.
 22. A conduit liningmechanism according to claim 20 wherein said trowelling means comprisesa frame supporting two sets of trowelling leaves tandemly thereon.
 23. Aconduit lining mechanism according to claim 22 wherein said trowellingmeans includes a central axially extending member from which radialelements extend to support said trowel elements.
 24. A conduit liningmechanism according to claim 23 wherein said trowelling means isattached to said lever arm at said central axially extending member. 25.A conduit lining mechanism according to claim 24 wherein said trowellingmeans is attached to said central axially extending member at a locationthereon intermediate said two sets of trowelling leaves.
 26. A conduitlining mechanism according to claim 25 wherein said lever arm ispivotally attached to said central axially extending member.
 27. Aconduit lining mechanism according to claim 26 wherein said centralaxially extending member is tubular and of substantially larger diameterthan said lever arm, said lever arm extending inside said member andpivotally secured to an inner flange in said member.
 28. A conduitlining mechanism according to claim 27 wherein said central axiallyextending member includes a balance weight longitudinally adjustabletherealong.